Cassava (Manihot esculenta Crantz) holds a significant place in Venezuelan cuisine, predominantly consumed fresh but also in various processed forms. In 1991, the production of cassava reached 381,069 tons, with 183,913 tons allocated for human consumption, including the production of “casabe,” a distinctive cassava bread. Recognizing the diverse applications of starch in industries such as food, pharmaceuticals, oil, and textiles, our study focuses on exploring the impact of extrusion cooking on the amylographic performance of cassava starch.
Materials and Methods
A commercial cassava starch underwent extrusion cooking in two Rheocord Torque Rheometers: Model 104 with a single rotating screw operating at 90 rpm and 150 °C, and Model 3000 with double co-rotating screws operating at 90 rpm and temperatures of 100 °C and 150 °C, with sample moisture contents ranging from 10% to 25%. Starch suspensions at 6.88% (w/w dry basis) were prepared and analyzed using a Brabender amylograph.
Results
The amylographic parameters presented in Table 1 showcase the profound impact of extrusion on cassava starch. Notably, the gelatinization temperature, initial and final, was influenced by the moisture content during extrusion, revealing a nuanced transformation in the starch granule structure. Extrusion led to a significant reduction in maximum viscosity (Vmax) compared to native starch, indicating potential macromolecule rupture and/or reorganization.
Extruded starches exhibited higher maximum viscosities at elevated temperatures, particularly at 25% moisture content, suggesting altered gelatinization dynamics. Swelling power, solubility, and water absorption capacity increased for extruded starches, highlighting the multifaceted impact of the extrusion process on starch properties. Of particular interest is the extruded starch at 10.21% moisture content in the double-screw extruder, which demonstrated superior swelling power and solubility.
Discussion
The reduction in Vmax values for all extruded starches implies modifications in starch macromolecules during the extrusion process. The observed decrease in stability during cooking, as indicated by the positive values of the stability index, suggests a heightened susceptibility of granules to shearing stress. This instability was notably less pronounced in starch processed at 10.21% moisture content by the double-screw extruder.
Retrogradation tendencies, assessed through the sedimentation index, showcased variations among extruded starches, with the lowest retrogradation observed in starch extruded at 25% moisture content by the double-screw extruder. Extrusion cooking increased the consistency of starches, with a notable rise in values compared to native starch.
Conclusions
Extrusion cooking emerges as a transformative process for cassava starch, influencing its structural and functional properties. The extrusion conditions, particularly moisture content, play a pivotal role in determining the extent of modifications. Starch extruded at 10.21% moisture content by the double-screw extruder demonstrated unique characteristics, including faster gelatinization onset, enhanced swelling power, and reduced retrogradation tendencies.
These findings provide valuable insights into optimizing extrusion conditions for cassava starch, opening avenues for tailored applications in various industries. The study contributes to the broader understanding of starch modification, offering a foundation for further research and innovations in starch-based products.